Orthopedic Extendable Rods

ABSTRACT

Embodiments herein are generally directed to extendable rods for use in orthopedic assemblies. In some embodiments, these implants may be used in conjunction with procedures to treat spinal deformities, including, but not limited to, early onset scoliosis.

FIELD OF THE INVENTION

The present invention relates to orthopedic extendable rods and methodsused to install and/or actuate these devices.

BACKGROUND OF THE INVENTION

Many types of spinal irregularities can cause pain, limit range ofmotion, or injure the nervous system within the spinal column. Theseirregularities can result from, without limitation, trauma, tumor, discdegeneration, and disease. One general example of a spinal irregularityis an abnormal curvature of the spine, for example, as exhibited withscoliosis, kyphosis, and/or lordosis. Scoliosis, a side-to-sidecurvature of the spine, can affect the dimensions of an individual'schest area, thereby impacting performance of internal organs such as thelungs and heart.

Treatment of scoliosis can include, for example, reducing the severityand preventing further progression of the irregularity through physicaltherapy, bracing, and/or surgery. Surgical procedures to treat scoliosiscan include spinal fusion, wherein the vertebrae are straightened andone or more rods are placed along the spinal column to maintain thealignment.

SUMMARY OF THE INVENTION

Some embodiments herein are directed to an extendable rod assembly thatcan include an elongate sleeve comprising a cannula extendingtherethrough; an actuating rod comprising an enlarged head disposedwithin the cannula and a body extending in a first direction, whereinthe enlarged head divides the cannula into a first chamber and a secondchamber; a fixed rod comprising an enlarged head disposed within thecannula and a body extending in a second direction; and a valve assemblyconfigured to control flow of a fluid between the first and secondchambers.

Other embodiments herein are directed to an extendable rod assembly thatcan include an elongate sleeve comprising a cannula extendingtherethrough; a valve assembly comprising a valve body disposed withinthe cannula and comprising an enlarged head, wherein the enlarged headdivides the cannula into a first chamber and a second chamber; a firstactuating rod comprising a first enlarged head disposed within the firstchamber and a body extending in a first direction, wherein the firstenlarged head divides the first chamber into a first sub-chamber and asecond sub-chamber; and a second actuating rod comprising a secondenlarged head disposed within the second chamber and a body extending ina second direction, wherein the second enlarged head divides the secondchamber into a third sub-chamber and a fourth sub-chamber; wherein thevalve assembly is configured to control flow of a fluid between thefirst and second sub-chambers, and between the third and fourthsub-chambers.

Some embodiments herein are directed to an extendable rod assembly thatcan include an elongate sleeve comprising a cannula extendinglongitudinally therethrough and a port, wherein the port is configuredto transfer a fluid in and out of the cannula; an actuating rodcomprising a locking member, wherein at least a portion of the actuatingrod is disposed within the cannula at a first end of the elongatesleeve; and a fixed rod comprising a head, wherein the head is disposedwithin cannula at a second end of the elongate sleeve.

Other embodiments herein are directed to a method of extending anextendable rod assembly, which can include providing an extendable rodassembly, wherein the extendable rod assembly has a first length;coupling the port with a fluid source; and introducing the fluid intothe cannula; wherein the fluid causes the actuating rod to translate atleast partially out of the cannula, thereby extending the extendable rodassembly to a second length that is greater than the first length.

Some embodiments herein are directed to an extendable rod assembly thatcan include an elongate sleeve comprising a conduit extendingtherethrough from a first end to a second end; an actuating rodcomprising a plurality of gear teeth and at least partially disposedwithin the first end of the conduit; a fixed rod at least partiallydisposed within the second end of the conduit; and a gear assemblyconfigured to actuate the actuating rod.

Other embodiments herein are directed to an extendable rod assembly thatcan include an elongate sleeve comprising a conduit extendingtherethrough and a housing member disposed thereon, wherein the housingmember is in fluid communication with the conduit; a gear assemblymounted in the housing member, an actuating rod at least partiallydisposed within the conduit and extending in a first direction; and afixed rod at least partially disposed within the conduit and extendingin a second direction; wherein a member of the gear assembly isconfigured to directly engage the actuating rod.

Still other embodiments herein are directed to an elongate sleevecomprising a conduit extending therethrough, and further comprising ahousing member in fluid communication with the conduit; a gear assemblydisposed within the housing member; an actuating rod at least partiallydisposed within the conduit and extending in a first direction, theactuating rod comprising a plurality of teeth configured to mesh with amember of the gear assembly; and a fixed rod at least partially disposedwithin the conduit and extending in a second direction.

Yet other embodiments herein are directed to a method of extending anextendable rod assembly, which can include providing a extendable rodassembly having a first length, coupling a driver with a drive member ofthe extendable rod assembly, and applying torque to the drive member ina first direction to thereby extend the extendable rod assembly to asecond length that is greater than the first length.

Further areas of applicability of the present disclosure will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating certain embodiments, are intended for purposes ofillustration only and are not intended to limit the scope of thedisclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIGS. 1A-H illustrate perspective and partial cross-sectional views ofan extendable rod assembly as described herein;

FIGS. 2A-D illustrate perspective and partial cross-sectional views ofan extendable rod assembly as described herein;

FIGS. 3A-G illustrate perspective and partial cross-sectional views ofan extendable rod assembly as described herein;

FIGS. 4A-C illustrate perspective and partial cross-sectional views ofan extendable rod assembly as described herein;

FIGS. 5A-C illustrate perspective views of an extendable rod assembly asdescribed herein; and

FIGS. 6A-F illustrate perspective views of an extendable rod assembly asdescribed herein.

DETAILED DESCRIPTION

Early onset scoliosis (EOS) refers to the occurrence of a lateral spinaldeviation in adolescents or children, for example, between four and nineyears old. In these instances, a spinal fusion may not be appropriatebecause it can impede the growth process. Rather, an expandable rod,sometimes referred to as a “growing rod,” may be implanted. These rodscan be implanted along the curved segment of the spine and may belengthened in situ, thereby growing along with the spinal column of theindividual. Often, growing rods may be lengthened on a standardschedule, such as every three to six months, through a surgicalprocedure. These repeated surgical procedures can be invasive andaccordingly can carry risks relating to wound healing and anesthesia,among other things. Additionally, the need for repeated surgicalprocedures can be time-consuming and costly. Accordingly, disclosedherein are new and improved spinal rods that can be extended in aminimally-invasive or non-invasive procedure.

Components of all of the devices disclosed herein can be made ofmaterials known to those skilled in the art, including metals (e.g.,titanium), metal alloys, polymers (e.g., poly ether ether ketone (PEEK),polyphenylene sulfone (PPSU), polysulfone (PSU), polycarbonate (PC),polyetherimide (PEI), polypropylene (PP), polyacetals, or mixtures orco-polymers thereof), allograft, and/or combinations thereof. In someembodiments, all components and/or all extendable rod assembliesdescribed herein may be non-ferromagnetic (e.g., may not exhibitmagnetic properties and/or may not be able to permanently produce amagnetic field). In these embodiments, individuals in whom the resultingassemblies are installed may advantageously be able to undergo medicalimaging techniques such as MRI. The components can also be machinedand/or manufactured using techniques known to those skilled in the art.For example, polymeric components may be injection-molded orblow-molded.

Turning now to FIGS. 1A-G, an extendable rod assembly 100 is illustratedin accordance with embodiments described herein. The extendable rodassembly 100 can include an elongate sleeve 2, an actuating rod 4, and afixed rod 6. The extendable rod assembly 100 can also include a valveassembly 7, as illustrated in FIG. 1E, for example. The extendable rodassembly 100 may include a length 24 as measured from a distal-most endof the actuating rod 4 to a distal-most end of the fixed rod 6.Advantageously, the length 24 of the extendable rod assembly 100 mayvary as the assembly 100 extends or retracts. In some embodiments, thelength 24 of the assembly 100 may be configured to increase by about 5cm to about 10 cm. In other embodiments, the length 24 of the assembly100 may be able to increase by at least 7 cm. In yet other embodiments,the length 24 of the assembly 100 may be configured to increase by afactor in the range of from about 10% to about 50%. In otherembodiments, the length 24 of the assembly 100 may be configured toincrease by a factor in the range of from about 20% to abut 30%. In yetother embodiments, the length of the assembly 100 may be configured toincrease by about 25%. As illustrated in FIG. 1A, the extendable rodassembly 100 can be configured to extend longitudinally in a straightline along its length 24. Those skilled in the art may appreciate thatother embodiments of extendable rod assemblies described herein may alsoinclude one or more of these length characteristics.

As used herein, the terms “proximal” and “distal” are utilized generallywith reference to the middle of the elongate sleeve of each extendablerod assembly. For example, the actuating rod 4 may have a proximal endand a distal end, wherein the proximal end is closer to the middle ofthe elongate sleeve than the distal end. For consistency, specificcomponents may also follow this directional convention, regardless oftheir particular disposition with respect to the elongate sleeve 2. Forexample, a particular component of the actuating rod 4 that is disposedwithin the elongate sleeve 2 may be described with the sameproximal-distal orientation as the actuating rod 4 as a whole,regardless of exactly where that particular component is disposed withinthe elongate sleeve 2.

As illustrated in FIG. 1A, the elongate sleeve 2 can be cylindrical(e.g., can include a circular transverse cross section, and a constantinner and/or outer diameter). In some embodiments, the elongate sleeve 2can have an outer diameter in the range of from about 5 mm to about 10mm. As illustrated in FIG. 1B, the elongate sleeve 2 can include acannula 28 extending longitudinally therethrough. The cannula 28 canhave a circular transverse cross-section and/or a constant diameter. Theelongate sleeve 2 can include a first end 8 and a second end 10. In someembodiments, each of the first and second ends 8, 10 can includeexternal threading. The first and second ends 8, 10 can be configured toengage or mate with first and second end caps 12, 14. For example, thefirst and second end caps 12, 14 can be configured to be disposed (e.g.,threaded) onto the first and second ends 8, 10. The second end cap 14can have some or all of the same features as the first end cap 12. Thefirst end cap 12 can be cylindrical, e.g., can have a constant outerdiameter. The first end cap 12 can also include a cannula passinglongitudinally therethrough, which can also have a circular transversecross-section. The first end cap 12 can include a proximal section 16and a distal section 18. The proximal section 16 can include a firstinner diameter and the distal section 18 can include a second innerdiameter. As illustrated in FIG. 1B, the inner diameter of the proximalsection 16 can be greater than the inner diameter of the distal section18. The difference in inner diameters between the proximal section 16and the distal section 18 may result in a ledge 17 at an interface wherethe two sections meet. The proximal section 16 can include interiorthreading. As described herein, the interior threading of the first endcap 12 can mate with the exterior threading of the elongate sleeve 2,thereby threading the first end cap 12 onto the elongate sleeve 2. Thedistal section 18 of the first end cap 12 can include an interiorcircumferential groove 20.

As illustrated in FIG. 1B, the interior circumferential groove 20 can beconfigured to receive a seal member 22 therein. The seal member 22, andany other seal members described herein, can be, for example, a squarering, an o-ring, or a gasket. In some embodiments, the seal memberincludes a square ring, and may be, for example, a wiper seal. In someembodiments, translating components (e.g., actuating rod) may include atleast one square ring seal member and stationary components (e.g., fixedrod) may include at least one o-ring seal member. The seal member mayalso include additional features, such as a one-way valve. Variousmaterials can be included in the seal member 22, and any other sealmembers described herein, such as thermoset polymers, thermoplasticpolymers, elastomeric polymers, and synthetic rubbers. Some examplesinclude, but are not limited to, ethylene propylene diene monomer (EPDM)rubber, fluoroelastomers (FKM), perfluoro-elastomers (FFKM), andtetrafluoro ethylene/propylene rubber (FEPM).

Turning to FIG. 1C, the actuating rod 4 can include an enlarged head 26and a body 30 extending from the enlarged head 26. The body 30 canextend in a first distal direction. The body 30 can include a cylinderhaving a constant outer diameter. In these embodiments, the body 30 mayhave a circular transverse cross-section, in other embodiments, the bodymay have a different cross-sectional shape, such as triangular, square,rectangular, pentagonal, or hexagonal. In some embodiments, the body 30can be solid. In other embodiments, the body 30 can be hollow (e.g., caninclude a cannula or other passageway extending at least partiallytherethrough). The diameter of the body 30 can vary, and may be, forexample, in the range of from about 3 mm to about 10 mm. In someembodiments, the diameter of the body 30 can be in the range of fromabout 4 mm to about 7 mm. As illustrated in FIG. 1C, the enlarged head26 can be configured to be disposed within the cannula 28 of theelongate sleeve 2. The outer diameter of the enlarged head 26 can be thesame as or slightly smaller than the inner diameter of the elongatesleeve 2. For example, the enlarged head 26 and the elongate sleeve 2may be engaged in a friction, interference, or slip fit. Additionally,the enlarged head 26 can have an outer diameter that is larger than anouter diameter of the body 30, as illustrated in FIGS. 1C-D.Accordingly, the enlarged head 26 can be configured to divide thecannula 28 into a first chamber 32 and a second chamber 34, illustratedin FIG. 1D. The outer diameter of the enlarged head 26 can also begreater than the inner diameter of the distal section 18 of the firstend cap 12. Thus, when the enlarged head 26 is disposed within theelongate sleeve 2 and the first end cap 12 is threaded onto the firstend 8, the enlarged head 26 may be trapped within the cannula 28. Theenlarged head 26 can also include at least one exterior circumferentialgroove 36. As illustrated in FIG. 1D, the enlarged head 26 can includetwo exterior circumferential grooves. The exterior circumferentialgroove(s) 36 can be configured to receive a seal member 38 therein. Insome embodiments, the seal member 38 is a square ring.

Those skilled in the art may appreciate that the actuating rod 4 may beconfigured to slide and/or translate longitudinally within the elongatesleeve 2. For example, the enlarged head 26 can travel between the firstend cap 12 and the stem 50 of the fixed rod 6. Accordingly, theextendable rod assembly 100 can be configured to transition between afirst configuration, wherein the assembly 100 is retracted, collapsed,shortened, un-expanded, and/or un-extended, and a second configuration,wherein the assembly 100 is lengthened, expanded, and/or extended. Inthe first configuration, the proximal surface 60 of the enlarged head 26can contact a proximal surface 72 of the stem 50. In this configuration,the first chamber 32 may be relatively large and the second chamber 34may be relatively small, as compared to the second configuration. In thesecond configuration, the distal surface of the enlarged head 26 cancontact the ledge 17 of the first end cap 12. In this configuration, thefirst chamber 32 may be relatively small and the second chamber 34 maybe relatively small, as compared to the first configuration. Thoseskilled in the art may appreciate that the assembly 100 may also becapable of numerous intermediate configurations, wherein the overalllength of the assembly 100 is greater than the fully retracted lengthand less than the fully extended length.

As illustrated in FIG. 1C, the fixed rod 6 can include an enlarged head40 and a body 42 extending from the enlarged head 40. The body 42 canextend in a second distal direction that is opposite of the body 30 ofthe actuating rod 4. The body 42 can include a cylinder having aconstant outer diameter. In some embodiments, the body 42 can be solid.In other embodiments, the body 42 can be hollow (e.g., can include acannula or other passageway extending at least partially therethrough).The diameter of the body 42 can vary, and may be, for example, in therange of from about 3 mm to about 10 mm. In some embodiments, thediameter of the body 42 can be in the range of from about 5 mm to about7 mm. In other embodiments, the diameter of the body 42 of the fixed rod6 can be the same as the diameter 30 of the actuating rod 4. Asillustrated in FIG. 1C, the enlarged head 40 can be configured to bedisposed within the cannula 28 of the elongate sleeve 2. The outerdiameter of the enlarged head 40 can be the same as or slightly smallerthan the inner diameter of the elongate sleeve 2. For example, theenlarged head 40 and the elongate sleeve 2 may be engaged in a frictionor slip fit. Additionally, the enlarged head 40 can have an outerdiameter that is larger than an outer diameter of the body 42, asillustrated in FIGS. 1C-D. The outer diameter of the enlarged head 40can also be greater than the inner diameter of a distal section 44 ofthe second end cap 14. Thus, when the enlarged head 40 is disposedwithin the elongate sleeve 2 and the second end cap 14 is threaded ontothe second end 10, the enlarged head 40 may be trapped within thecannula 28. The enlarged head 40 can include at least one exteriorcircumferential groove 46. As illustrated in FIG. 1D, the enlarged head40 can include two exterior circumferential grooves. The exteriorcircumferential groove(s) 46 can be configured to receive a seal member48 therein. In some embodiments, the seal member 48 is a square ring. Asillustrated in FIG. 1D, the fixed rod 6 may further include a stem 50.The stem 50 may extend proximally from the enlarged head 40. The shapeof the stem 50 can vary. In some embodiments, it may be cylindrical(e.g., the stem 50 may have a circular transverse cross-sectionalshape). In other embodiments, it may be rectangular or may take on someother polygonal shape. As illustrated in FIG. 1D, the transversecross-sectional area of the stem 50 may be smaller than a transversecross-sectional area of the enlarged head 40. In embodiments where thestem 50 is cylindrical, the stem 50 may have a smaller diameter than thediameter of the enlarged head 40. Advantageously, the stem 50 may beused to maintain a gap between the actuating rod 4 and the fixed rod 6,thereby preventing the formation of a seal between these two members.

The extendable rod assembly 100 may also include a valve assembly. Thevalve assembly can be configured to control, regulate, and/or permitflow of a fluid between the first and second chambers 32, 34. In someembodiments, the extendable rod assembly 100 may include a needle valveassembly. Advantageously, the valve assembly may include an automaticvalve that regulates flow in response to changes in fluid pressure. Insome embodiments, the valve assembly can include a hydraulic orpneumatic actuation mechanism. Various fluids may be used in these valveassemblies, and may be selected on the basis of various factors,including, but not limited to compressibility, viscosity, and thermalconductivity, as well as consideration of the expected load or weightexerted on the assembly 100. Non-limiting examples of suitable fluidsinclude air and saline.

Turning to FIG. 1E, one embodiment of a valve assembly 7 is illustrated.The valve assembly 7 can include a conduit 52 and a cavity 56 on aproximal portion of the body of the actuating rod 4, and a valve body54. The conduit 52 can include an opening 58 on a proximal surface 60 ofthe enlarged head 26 of the actuating rod 4. The conduit 52 can extendlongitudinally through the enlarged head 26 and a portion of the body 30so as to intersect with the cavity 56. The conduit 52 can be in fluidcommunication with the cavity 56 and the second chamber 34.

The cavity 56 can be located at a proximal end of the body 30 of theactuating rod 4. The cavity 56 can extend along a transverse axis of theactuating rod 4. The cavity 56 can extend from a first opening 62 to asecond opening 64, wherein both openings are on the body 30 of theactuating rod 4. The cavity 56 can be in fluid communication with thefirst chamber 32. The cavity 56 can have a shape that is configured toconform to the shape of the valve body 54. As illustrated in FIG. 1E,the cavity 56 can include a tapered portion, a cylindrical portion, anda threaded portion. The tapered portion of the cavity 56 may have thesame dimensions as the tapered portion of the tapered portion of thevalve body 54, described further herein. In some embodiments, theconduit 52 can intersect the tapered portion of the cavity 56.

The valve body 54 can be disposed within the cavity 56. The valve body54 can include a stem 66 and a base 68. The stem 66 can include atapered tip. As illustrated in FIG. 1E, the stem 66 can include afrustoconical tip. The stem 66 may be configured to be received withinthe tapered portion of the cavity 56. As illustrated in FIG. 1E, forexample, the stem 66 may block the passage of fluid between the firstchamber 32 and the second chamber 34. In particular, the tip of the stem66 may block the second opening 64 and the conduit 52. The base 68 canbe compressible, e.g., the volume occupied by the base 68 may bereversibly decreased. In some embodiments, the base 68 can include anelastic material (e.g., an elastomer). In other embodiments, the base 68can include a spring member. Example materials that can be used for thebase 68 include, but are not limited to, synthetic polymers such asnylon and other polyamides, silicones, polyurethanes, polyesters, andpolyalkylene oxides. The base 68 may have a cylindrical shape and beconfigured to be received within the cylindrical portion of the cavity56. In other embodiments, the base 68 may have a different shape.

As illustrated in FIG. 1E, the valve assembly 7 can further include afastener 70. The fastener 70 can be configured to be received within thecavity 56 (e.g., the threaded portion). In some embodiments, thefastener 70 may be a set screw. In these embodiments, the fastener 70may be configured to be threaded into the threaded portion of the cavity56. In other embodiments, the fastener 70 may not include externalthreading (e.g., the fastener 70 may include a cam lock). In theseembodiments, the cavity 56 may not include internal threading, but mayinclude another feature configured to engage the fastener 70 (e.g., acam groove). Advantageously, the fastener 70 may be configured to securethe valve body 54 within the cavity 56.

Embodiments herein are also directed to methods of installing theextendable rod assembly 100. In use, the first and second chambers 32,34 may be filled with a fluid. As described herein, the particular fluidmay be selected on the basis of the anticipated load that the extendablerod assembly 100 will bear, among other factors. The extendable rodassembly 100 may be installed in a retracted, collapsed, shortened, orun-extended configuration, using techniques known to those skilled inthe art. In this configuration, the proximal surface 60 of the enlargedhead 26 of the actuating rod 4 may rest against or be adjacent to theproximal surface 72 of the stem 50.

In some embodiments, the extendable rod assembly 100 may be used inconjunction with one or more other devices, including but not limited toa bone screw, intervertebral cage, artificial disc, stabilizing plate,or other prosthetics, to treat a spinal irregularity. In embodimentswhere the extendable rod assembly 100 is used to treat scoliosis or EOS,it may be configured to be coupled to a posterior section of a spine. Insome embodiments, two assemblies 100 may be installed, with one on eachside of a spinal column. The extendable rod assembly 100 may be coupled,fastened, or secured to a posterior section of a bone (e.g., a vertebraor a rib) through one or more fasteners (e.g., screws and/or hooks). Inthese embodiments, the fastener(s) may be installed prior to theextendable rod assembly 100. For example, pedicle screws may beinstalled in pedicles of a first (e.g., superior) vertebra above thecurvature and a second (e.g., inferior) vertebra below the curvature.Any pedicle screws known in the art and configured to receive a rod maybe used, including but not limited to monoaxial and polyaxial pediclescrews. After the fasteners are installed, the extendable rod assembly100 may be installed by coupling the actuating rod 4 and the stationaryrod 6 with the fasteners. In some embodiments, the actuating rod 4and/or the stationary rod 6 may be secured or anchored, e.g., unable topivot, rotate, and/or translate, relative to the fasteners and therespective vertebrae. In some embodiments, the actuating rod 4 may becoupled with the superior vertebra and the stationary rod 6 may becoupled with the inferior vertebra. However, the extendable rod assembly100 can advantageously be installed with either rod extending in thesuperior direction, and vice versa. Thus, in other embodiments, theactuating rod 4 may be coupled with an inferior vertebra and thestationary rod 6 may be coupled with a superior vertebra.

As described herein, growing rods may be used to treat early onsetscoliosis in children who may still be growing. Thus, afterinstallation, the rod may need to be extended or lengthened in order toaccommodate the child's growth. Advantageously, the extendable rodassembly 100 may be configured to extend and/or lengthen automatically,in vivo, without surgical or clinical intervention. In use, as the spinegrows, the first and second vertebrae may be pulled apart, resulting inthe actuating rod 4 and the fixed rod 6 being pulled apart. The fixedrod 6 may already be seated in the second end cap 14, and may thereforebe unable to translate within the elongate sleeve 2 in the direction ofthe applied force. In contrast, the actuating rod 4 may be pulled in thedistal (e.g., outward) direction, resulting in increased pressure in thefirst chamber 32 and reduced pressure in the second chamber 34. Thevalve assembly 7 may be used to equalize the pressure in the first andsecond chambers 32, 34. As the pressure increases in the first chamber32, a force may be exerted on the valve body 54, which may cause thebase 68 to compress, as illustrated in FIGS. 1G-H. Consequently, thestem 66 may be pushed down within the cavity 56 so that it is no longerblocking the second opening 64 and/or the conduit 52. Fluid may then beallowed to flow between the first chamber 32 and the second chamber 34,via the cavity 56 and conduit 52. As fluid flows between the first andsecond chambers 32, 34, the pressure within the two chambers may beequalized. Advantageously, as the spine grows, the extendable rodassembly 100 can continue to extend automatically in this manner. Inaddition to avoiding complications due to repeated invasive procedures,the automatic adjustment of the extendable rod assembly 100 mayeliminate or reduce the need for repeated doctor's visits. This featuremay be particularly helpful in situations where patients live far awayfrom their doctors and/or are unable to visit their doctor on a regularbasis.

Turning now to FIGS. 2A-D, an extendable rod assembly 200, which mayoptionally be referred to as a curved rod assembly, is illustrated inaccordance with embodiments described herein. The extendable rodassembly 200 can include an elongate sleeve 202, an actuating rod 204,and a fixed rod 206. As described further herein, the extendable rodassembly 200 may advantageously be configured to extend longitudinallyin a curved line.

As illustrated in FIG. 2B, the actuating rod 204 can include a two-piecebody. The two-piece body can include a first segment 210 and a secondsegment 212, wherein the first segment 210 extends distally from thesecond segment 212. The first segment 210 can be pivotably coupled tothe second segment 212 by a joint (e.g., a ball and socket joint). Thefirst segment 210 can include a proximal portion 214 and the secondsegment 212 can include a distal portion 218. As described furtherherein, the first segment 210 can include a socket and the secondsegment 212 can include a rounded protrusion. In other embodiments, thefirst segment 210 can include a rounded protrusion and the secondsegment 212 can include a socket. As illustrated in FIGS. 2C-D, theproximal portion 214 of the first segment 210 can include a socket 216.The proximal portion 214 of the first segment 210 can include a firstarm 224 and a second arm 226 defining the socket 216 therebetween. Thefirst and second arms 224, 226 can be separated by a transverse channelor void 228 that extends through the proximal portion from a first outersurface to a second outer surface, intersecting the socket 216.Accordingly, the transverse channel or void 228 may be in fluidcommunication with the socket 216.

The distal portion 218 of the second segment 212 can include a neck 220and a rounded protrusion 222 extending from the neck 220. The socket 216can be configured to receive the rounded protrusion 222 therein. In someembodiments, the socket 216 can include a rounded inner surface. Thecurvature of the rounded inner surface can match (e.g., equal) thecurvature of the rounded protrusion 222. A proximal portion of the firstsegment 210 (e.g., a proximal portion of the first and second arms 224,226) may further include a ringed protrusion or rim 230. The rim 230 candefine a passageway having a width that is less than a diameter of therounded protrusion 222. The rounded protrusion 222 may thus be secured,trapped, or contained within the socket 216. However, the roundedprotrusion 222 may also be configured to pivot or rotate within thesocket 216.

The elongate sleeve 202 may take the shape of a curved tube and mayextend longitudinally along a curved line. As illustrated in FIGS. 2A-B,the first segment 210 of the actuating rod 204 may also be curved, e.g.,may extend longitudinally along a curved line. The first segment 210 mayfollow the same curvature as the elongate sleeve 202. In someembodiments, the actuating rod 204 and the elongate sleeve 202 may beconcentric. The fixed rod 206 may also have a body portion 208 that canextend longitudinally along a straight or curved line. In someembodiments, the elongate sleeve 202, first segment 210 of the actuatingrod 204, and/or the body portion 208 of the fixed rod 206 may bemalleable (e.g., contourable, flexible, and/or bendable) and/or thecurvature of these elements may be adjustable. Except as otherwisedescribed, the extendable rod assembly 200 and its components mayadditionally include some or all of the same features (e.g., valveassembly 7) as specified with respect to the extendable rod assembly100.

In use, the extendable rod assembly 200 may be installed, e.g., along aspine, as described herein with respect to extendable rod assembly 100.The actuating rod 204 may be pulled distally (e.g., outward) to extendor lengthen the assembly 200. As the actuating rod 204 travels along acurved path (e.g., as dictated by the curvature of the elongate cannula202), the first and second segments 210, 212 may pivot with respect toone another, transferring force along the actuating rod 204 and/orenabling the actuating rod 204 to slide or translate smoothly.Advantageously, the jointed actuating rod 204 may enable or facilitatethe use of curved assemblies, which may more closely match the contouror curvature of an individual's spine.

Turning now to FIGS. 3A-G, an alternative embodiment featuring anextendable rod assembly 300 is illustrated. The extendable rod assembly300 can include an elongate sleeve 302, an actuating rod 304, and afixed rod 306. The extendable rod assembly 300 can also include a valveassembly 307, as illustrated in FIG. 3E. The elongate sleeve 302 caninclude a first end 308, a second end 310, and a cannula 358 extendingtherethrough. In some embodiments, each of the first and second ends308, 310 can include external threading. In some embodiments, the firstand second ends 308, 310 may be symmetrical. In other embodiments, theymay be asymmetrical. The first and second ends 308, 310 can beconfigured to engage or mate with first and second end caps 312, 314.For example, the first and second end caps 312, 314 can be configured tobe disposed (e.g., threaded) onto the first and second ends 308, 310.The second end cap 314 can include some or all of the features as thefirst end cap 312. In other embodiments, the second end cap 314 caninclude some or all of the features as the first and/or second end caps12, 14 as described herein with respect to the extendable rod assembly100.

In some embodiments, the second end 310 of the elongate sleeve 302 mayinclude a constricted section 380, as illustrated in FIG. 3G. Theconstricted section 380 can include an inner diameter that is smallerthan adjacent of the elongate sleeve 302 on either side of theconstricted section 380. As a result, the constricted section 380 may bebounded by a first ledge 382 and a second ledge 384. In someembodiments, the constricted section 380 is next to (e.g., proximal to)or located within the exteriorly-threaded section of the second end 310.The outer diameter of the constricted section 380 may be the same ordifferent as other sections of the elongate sleeve 302. As describedherein, the constricted section 380 may inhibit translational movementof the fixed rod 306 and/or may prevent contact between the actuatingrod 304 and fixed rod 306, thereby preventing formation of a sealbetween these members.

As illustrated in FIG. 3B, the first end cap 312 can include a hollowtube 316 and a rotatable stopper 318. As illustrated in FIG. 3C, thehollow tube 316 can include a first open end 320, a second open end 322,and an at least partially threaded inner surface 324. The hollow tube316 can have an annular or ring-shaped transverse cross section. Thefirst open end 320 can have an inner diameter that is equal to an innerdiameter of the second open end 322. In some embodiments, the hollowtube 316 can have a constant inner and/or outer diameter. The threadedinner surface 324 may be configured to mate with the external threadingon the first end 308 of the elongate sleeve 302. For example, the hollowtube 316 may be threaded onto the first end 308 of the elongate sleeve302. As illustrated in FIG. 3C-D, the first open end 320 may beconfigured to contact or abut a portion of the rotatable stopper 318(e.g., the enlarged head 326, described further herein).

As illustrated in FIG. 3C, the rotatable stopper 318 can include anenlarged head 326, an intermediate section 328, and a body 330. Theenlarged head 326 may have a larger outer diameter than that of theintermediate section 328, and the intermediate section 328 may have alarger outer diameter than that of the body 330. Accordingly, therotatable stopper 318 may include a ledge 350 at an interface betweenthe enlarged head 326 and intermediate section 328, and a ledge 352 atan interface between the intermediate section 328 and the body 330. Therotatable stopper 318 can include a cannula 332 extending longitudinallytherethrough. The intermediate section 328 and the body 330 can beconfigured to be received within the hollow tube 316. At least a portionof an outer surface of the body 330 may be configured to engage at leasta portion of an inner surface of the first end 308 of the elongatesleeve 302. As illustrated in FIGS. 3B-C, the body 330 of the rotatablestopper 318 may be inserted into the first end 308 of the elongatesleeve 302. In some embodiments, the rotatable stopper 318 and theelongate sleeve 302 may be engaged in an interference, friction, or slipfit. For example, the rotatable stopper 318 may be configured to rotate,pivot, or twist within the elongate sleeve 302. The rotatable stopper318 may further include one or more seal members. As illustrated inFIGS. 3B-C, the enlarged head 326 of the rotatable stopper 318 caninclude at least one interior circumferential groove 334 configured toreceive a seal member 336. As illustrated in FIG. 3B, the enlarged head326 can include two circumferential grooves 334 and two seal members 336disposed therein. The intermediate portion 328 can include an exteriorcircumferential groove 338 configured to receive a seal member 340therein. The body portion 330 can also include an exteriorcircumferential groove 342 configured to receive a seal member 344therein. Any of the seal members described herein, e.g., wiper seals,can be used as seal members 336, 340, and 344.

The body 330 of the rotatable stopper can include at least onelongitudinal groove 346, as illustrated in FIG. 3D. In some embodiments,two, three, four, or more longitudinal grooves can be disposedcircumferentially about the body 330. As illustrated in FIG. 3D, aninternal surface of the first end 308 of the elongate sleeve 302 canalso include at least one longitudinal groove 348. In some embodiments,two, three, four, or more longitudinal grooves can be disposedcircumferentially about the interior of the first end 308. Thelongitudinal grooves on the interior surface of the elongate sleeve 302can be configured to align with the longitudinal grooves on the exteriorsurface of the body 330.

When assembled, the hollow tube 316 may be threaded onto the first end308 of the elongate sleeve 302. The hollow tube 316 may not completelyoverlap the first end 308 of the elongate sleeve 302; instead, these twoelements may be longitudinally staggered. The first open end 320 of thehollow tube 316 may extend distally as compared to a first end face 354of the elongate sleeve 302, as illustrated in FIG. 3D. The body 330 ofthe rotatable stopper 318 may be inserted into the first end 308 of theelongate sleeve 302. As described herein, the body 330 may be engagedwith the elongate sleeve 302 in a slip fit and may be configured torotate within the elongate sleeve 302. A portion of the enlarged head326 (e.g., ledge 350) may abut the first open end 320 of the hollow tube316. As illustrated in FIG. 3D, this configuration may result in thecreation of a gap 356 between the first end face 354 of the elongatesleeve 302 and the ledge 352 of the enlarged head 326.

In use, when the elongate grooves 346, 348 on the rotatable stopper 318and the elongate sleeve 302 are not in alignment, the cannula 358 maynot be in fluid communication with the gap 356. However, when therotatable stopper 318 is rotated, the elongate grooves 346, 348 may bealigned, thereby allowing fluid communication between the cannula 358and the gap 356 and effectively lengthening the cannula 358. Asdescribed herein with respect to the valve assembly 7 of extendable rodassembly 100, a fluid may be added to the cannula (e.g., first and/orsecond chambers 32, 34) at a particular pressure based on, among otherthings, the anticipated load that will be borne by the extendable rodassembly 100 in situ. The first end cap 312 described in the presentembodiment advantageously permits the pressure in the assembly to beadjusted by twisting or rotating the rotatable stopper 318. Accordingly,the pressure may be easily varied, either before, during, or afterinstallation.

Turning to FIG. 3E-F, the valve assembly 307 can include a duct 364 anda cavity 360 on a proximal portion of the actuating rod 304, and a valvebody 362. As described herein with respect to the actuating rod 4 of theextendable rod assembly 100, the actuating rod 304 may include anenlarged head 366, which can be disposed within the elongate sleeve 302.The outer diameter of the enlarged head 366 may be equal to or slightlysmaller than the inner diameter of the elongate sleeve 302, such thatthese two components may be engaged in a friction, interference, or slipfit. As illustrated in FIG. 3F, the enlarged head 366 may be configuredto divide the cannula 358 into a first chamber 368 and a second chamber370. The duct 364 may be in fluid communication with the first chamber368 and the cavity 360, and the cavity 360 may be in fluid communicationwith the second chamber 370. In some embodiments, the duct 364 canextend from an outer surface (e.g., a side wall) of the actuating rod304 to the cavity 360. The cavity 360 can extend at least partiallyalong a longitudinal axis of the actuating rod 304.

The valve body 362 may regulate fluid flow between the first and secondchambers 368, 370. As illustrated in FIGS. 3E-F, the valve body 362 caninclude a first extension member 363 extending proximally from the fixedrod 306. In some embodiments, the first extension member 363 can extendfrom a proximal-most surface 378 of the fixed rod 306. The firstextension member 363 can be slideably disposed within the cavity 360.The first extension member 363 can include a first longitudinal cannula372 extending at least partially through the first extension member 363.The first extension member 363 can also include a plurality oftransverse conduits 374 in fluid communication with the firstlongitudinal cannula 372. In some embodiments, the first extensionmember 363 may include a number of transverse conduits 374 in the rangeof from about ten to about fifty. In other embodiments, the firstextension member 363 may include a number of transverse conduits 374 inthe range of from about twenty to about thirty. The transverse conduits374 may be spaced apart longitudinally in regular intervals. Eachtransverse conduit 374 can extend from an outer surface of the firstextension member 363 to the first longitudinal cannula 372. Thetransverse conduit 374 can take on a plurality of different shapes. Forexample, it may be a pin hole (e.g., circular opening) or a slot (e.g.,rectangular opening). In some embodiments, each transverse conduit 374can include a semicircular slot (e.g, semicircular as viewed along atransverse plane of the first extension member 363). In otherembodiments, each transverse conduit 374 can extend along at least 25%of an outer circumference of the first extension member 363. In someembodiments, the first extension member 363 can include a plurality oftransverse channels or grooves 376, as illustrated, for example, in FIG.3E. The grooves 376 can extend circumferentially around the firstextension member 363. Each transverse conduit 374 may be situated withina groove 376. Except as otherwise described, the extendable rod assembly300 and its components may additionally include some or all of the samefeatures as specified with respect to the extendable rod assembly 100and/or 200. Additionally, those skilled in the art may appreciate thatthe valve assembly 307 and/or the first end cap 312, among other things,may be incorporated into the extendable rod assembly 100 and/or 200.

In use, the extendable rod assembly 300 may be installed, e.g.,posteriorly along a spine, in a retracted, collapsed, or un-extendedconfiguration as described herein with respect to the extendable rodassembly 100, for example. As the spine grows or lengthens, the distancebetween the first and second vertebrae to which the extendable rodassembly 300 is coupled or secured may increase, resulting in theactuating rod 304 and the fixed rod 306 being pulled apart. The fixedrod 306 may be seated in the second end cap 314, as illustrated in FIG.3G. The constricted section 380 may inhibit the fixed rod 306 fromtranslating within the elongate sleeve 302. In contrast, the actuatingrod 304 may be pulled in the distal (e.g., outward) direction, resultingin increased pressure in the first chamber 368 and reduced pressure inthe second chamber 370. The valve assembly 307 may be configured toequalize the pressure in the first and second chambers 368, 370. As theactuating rod 304 is pulled distally (e.g., outward), the pressure inthe first chamber 368 may increase until the duct 364 enters fluidcommunication with a transverse conduit 374, as illustrated in FIG. 3G.As that point, fluid from the first chamber 368 is allowed to flow tothe second chamber 370 through the transverse conduit 374 and the firstlongitudinal cannula 372. The groove 376 may promote channeling thefluid into the transverse conduit 374. The pressure in the first andsecond chambers 368, 370 may then be equalized. As the spine continuesto grow, the pressure differential between the first and second chambers368, 370 may increase until the next transverse conduit 374 reaches theduct 364. Advantageously, as the spine grows or lengthens, theextendable rod assembly 300 can continue to extend automatically in thismanner.

Some embodiments can include two actuating rods and a valve assemblyhaving two extension members. Turning now to FIGS. 4A-C, an alternativeembodiment featuring an extendable rod assembly 400 is illustrated. Theextendable rod assembly 400 can include an elongate sleeve 402, a firstactuating rod 404, and a second actuating rod 406. The two actuatingrods 404, 406 may both be configured to translate within the elongatesleeve 402 to increase the overall length of the extendable rod assembly400. The extendable rod assembly 400 can also include a valve assembly407, as illustrated in FIGS. 4B-C. The elongate sleeve 402 can include afirst end 408, a second end 410, and a cannula 411 extendingtherethrough. The elongate sleeve 402 can be cylindrical (e.g., caninclude a circular transverse cross section and a constant inner and/orouter diameter). In some embodiments, the elongate sleeve 402 may havean outer diameter in the range of from about 5 mm to about 10 mm. Thecannula 411 can have a circular transverse cross-section and/or aconstant diameter. In some embodiments, the first and second ends 408,410 can include external threading as illustrated in FIG. 4A, forexample. In some embodiments, the first and second ends 408, 410 may besymmetrical. In other embodiments, they may be asymmetrical. The firstand second ends 408, 410 can be configured to engage or mate with firstand second end caps 412, 414. The first and second ends 408, 410 can beconfigured to engage or mate with first and second end caps 412, 414.For example, the first and second end caps 412, 414 can be configured tobe disposed (e.g., threaded) onto the first and second ends 408, 410.The second end cap 414 can include some or all of the features as thefirst end cap 412. As illustrated in FIGS. 4A-C, the first and secondend caps 412, 414 can include the same features as described herein withrespect to the first end cap 312 of extendable rod assembly 300. Forexample, the first end cap 412 can include a hollow tube 416 and arotatable stopper 418. The second end cap 414 may also include a hollowtube 417 and a rotatable stopper 419. In other embodiments, the firstand/or second end cap 412, 414 can include some or all of the featuresas the first and/or second end caps 12, 14 as described herein withrespect to the extendable rod assembly 100.

As illustrated in FIGS. 4B-C, the valve assembly 407 may include a valvebody 420 configured to be disposed or situated within the cannula 411.The valve body 420 may include an enlarged head 422, a first extensionmember 428 extending from the enlarged head 422 in a first direction,and a second extension member 430 extending from the enlarged head 422in a second direction opposite of the first extension member 428. Theouter diameter of the enlarged head 422 can be the same as or slightlysmaller than the inner diameter of the elongate sleeve 402. For example,the enlarged head 422 and the elongate sleeve 402 may be engaged in afriction or slip fit. Accordingly, the enlarged head 422 of the valvebody 420 may be configured to divide the cannula 411 into a firstchamber 424 and a second chamber 426. The first and second chambers 424,426 may not be in fluid communication with each other. In someembodiments, the valve body 420 may further include a first stemdisposed between the first extension member 428 and the enlarged head422 and a second stem disposed between the second extension member 430and the enlarged head 422. The first and second stems may each have asmaller diameter than that of the enlarged head 422 and/or may beconfigured to prevent the first and second actuating rods 404, 406 fromcontacting the enlarged head 422 and forming a seal. The enlarged head422 can include at least one exterior circumferential groove 436. Theexterior circumferential groove(s) may be configured to receive a sealmember 438 therein. In some embodiments, the seal member 438 is ano-ring. In other embodiments, the seal member 438 may have one or moreproperties as described herein with respect to seal member 22 ofextendable rod assembly 100. In some embodiments, the enlarged head 422can include two exterior circumferential grooves and two o-rings seatedtherein, as illustrated in FIGS. 4B-C.

The first and/or second extension members 428, 430 may have some or allof the same features described herein with respect to the firstextension member 363 of the extendable rod assembly 300. For example,the first extension member 428 can include a first longitudinal cannulaextending at least partially therethrough. The first extension member428 can also include a plurality of transverse conduits 432 in fluidcommunication with the first longitudinal cannula. In some embodiments,the first extension member 428 may include a number of transverseconduits 432 in the range of from about ten to about fifty. In otherembodiments, the first extension member 428 may include a number oftransverse conduits 432 in the range of from about twenty to aboutthirty. The transverse conduits 432 may be spaced apart longitudinallyin regular intervals. Each transverse conduit 432 may extend from anopening on an outer surface of the first extension member 428 to thefirst longitudinal cannula. The transverse conduit 432 can take on aplurality of different shapes. For example, it may be a pin hole (e.g.,circular opening) or a slot (e.g., rectangular opening). In someembodiments, each transverse conduit 432 can include a semicircular slot(e.g., semicircular as viewed along a transverse plane of the firstextension member 428). In other embodiments, each transverse conduit 432can extend along at least 25% of an outer circumference of the firstextension member 428. In some embodiments, the first extension member428 can include a plurality of transverse channels or grooves 434, asillustrated in FIG. 4C. The grooves 434 can extend circumferentiallyaround the first extension member 428. Each transverse conduit 432 maybe situated within a groove 434. The second extension member 430 may beidentical (e.g., symmetrical) to the first extension member 428. Forexample, the second extension member 430 can include a secondlongitudinal cannula and a plurality of transverse conduits in fluidcommunication with the second longitudinal cannula.

The first actuating rod 404 may include some or all of the same featuresas the first actuating rod 304 in the extendable rod assembly 300. Insome embodiments, the first actuating rod 404 may be identical to thefirst actuating rod 304. The first actuating rod 404 may include, forexample, an enlarged head 440 and a body 442 extending from the enlargedhead 440. The enlarged head 440 can be configured to be disposed,situated, or received within a portion of the cannula 411 of theelongate sleeve 402 (e.g., within the first chamber 424). The outerdiameter of the enlarged head 440 can be the same as or slightly smallerthan the inner diameter of the elongate sleeve 402. For example, theenlarged head 440 and the elongate sleeve 402 may be engaged in aninterference, friction, or slip fit. Additionally, the enlarged head 440can have an outer diameter that is larger than an outer diameter of thebody 442, as illustrated in FIGS. 4B-C. Accordingly, the enlarged head440 can be configured to divide the first chamber 424 into a firstsub-chamber 444 and a second sub-chamber 446, illustrated in FIG. 4C.The outer diameter of the enlarged head 440 can also be greater than theinner diameter of the distal section of the rotatable stopper 418. Thus,when the enlarged head 440 is disposed within the first chamber 424 andthe first end cap 412 is engaged with the first end 408, the enlargedhead 440 may be trapped within the first chamber 424. The enlarged head440 can also include at least one exterior circumferential groove 448.As illustrated in FIGS. 4B-C, the enlarged head 440 can include twoexterior circumferential grooves. The exterior circumferential groove(s)448 can be configured to receive a seal member 450 therein. In someembodiments, the seal member 450 is a square ring.

A proximal portion of the first actuating rod 404 may also include aduct (not shown, but analogous to duct 364 of extendable rod assembly300) and a cavity 452. The duct may be in fluid communication with thefirst sub-chamber 444 and the cavity 452, and the cavity 452 may be influid communication with the second sub-chamber 446. In someembodiments, the duct can extend from an outer surface (e.g., a sidewall) of the first actuating rod 404 to the cavity 452. The cavity 452can extend at least partially along a longitudinal axis of the firstactuating rod 404, and may be configured to receive at least a portionof the first extension member 428 therein. As illustrated in FIG. 4C,the first extension member 428 of the valve body 420 may extend throughthe first chamber 424 and into the cavity 452. The first extensionmember 428 may be configured to slide or translate along or within thecavity 452.

The second actuating rod 406 may include some or all of the samefeatures as the first actuating rod 404. In some embodiments, the secondactuating rod 406 may be identical to the first actuating rod 404. Thesecond actuating rod 406 may include, for example, an enlarged head 454and a body 456 extending from the enlarged head 454. The enlarged head454 can be configured to be disposed, situated, or received within aportion of the cannula 411 of the elongate sleeve 402 (e.g., within thesecond chamber 426). The outer diameter of the enlarged head 454 can bethe same as or slightly smaller than the inner diameter of the elongatesleeve 402. For example, the enlarged head 454 and the elongate sleeve402 may be engaged in an interference, friction, or slip fit.Additionally, the enlarged head 454 can have an outer diameter that islarger than an outer diameter of the body 456, as illustrated in FIGS.4B-C. Accordingly, the enlarged head 454 can be configured to divide thesecond chamber 426 into a third sub-chamber 458 and a fourth sub-chamber460, illustrated in FIG. 4C. The outer diameter of the enlarged head 454can also be greater than the inner diameter of the distal section of therotatable stopper 419. Thus, when the enlarged head 454 is disposedwithin the second chamber 426 and the second end cap 414 is engaged withthe second end 410, the enlarged head 454 may be trapped within thesecond chamber 426. The enlarged head 454 can also include at least oneexterior circumferential groove 462. As illustrated in FIGS. 4B-C, theenlarged head 454 can include two exterior circumferential grooves. Theexterior circumferential groove(s) 462 can be configured to receive aseal member 464 therein. In some embodiments, the seal member 464 is asquare ring.

A proximal portion of the second actuating rod 406 may also include aduct 466 and a cavity 468. The duct 466 may be in fluid communicationwith the third sub-chamber 458 and the cavity 468, and the cavity 468may be in fluid communication with the fourth sub-chamber 460. In someembodiments, the duct 466 can extend from an outer surface (e.g., a sidewall) of the second actuating rod 406 to the cavity 468. The cavity 468can extend at least partially along a longitudinal axis of the secondactuating rod 406, and may be configured to receive at least a portionof the second extension member 430 therein. As illustrated in FIG. 4C,the second extension member 430 of the valve body 420 may extend throughthe second chamber 426 and into the cavity 468. The second extensionmember 430 may be configured to slide or translate along or within thecavity 468.

The valve assembly 407 can include the valve body 420, duct and cavity452 on the first actuating rod 404, and duct 466 and cavity 468 on thesecond actuating rod 406. The valve body 420 may regulate fluid flowbetween the first and second sub-chambers 444, 446, and between thethird and fourth sub-chambers 458, 460. In use, the extendable rodassembly 400 may be installed, e.g., posteriorly along a spine, in aretracted, collapse, or un-extended configuration as described hereinwith respect to the extendable rod assembly 100 and/or 300, for example.As the spine grows or lengthens, the distance between the first andsecond vertebrae to which the extendable rod assembly 400 is coupled orsecured may increase, resulting in the first actuating rod 404 and thesecond actuating rod 406 being pulled apart. In contrast to theextendable rod assemblies 100 and/or 300, both actuating rods 404, 406may be configured to translate within or along the elongate sleeve 402in the direction of the applied force. For example, where the firstactuating rod 404 is coupled with a superior vertebra and the secondactuating rod 406 is coupled with an inferior vertebra, the firstactuating rod 404 may extend, translate, or slide in the superiordirection and the second actuating rod 406 may extend, translate, orslide in the inferior direction.

As described herein with respect to the extendable rod assembly 300,when the first actuating rod 404 is pulled in a first distal or outward(e.g., superior) direction, pressure in the first sub-chamber 444 mayincrease and pressure in the second sub-chamber 446 may decrease.Similarly, when the second actuating rod 406 is pulled in a seconddistal or outward (e.g., inferior) direction, pressure in the thirdsub-chamber 458 may increase and pressure in the fourth sub-chamber 460may decrease. The valve assembly 407 may be configured to equalize thepressure in the four sub-chambers. As the first actuating rod 404 ispulled in a first distal direction, the pressure in the firstsub-chamber 444 may increase until the duct (not shown) enters fluidcommunication with a transverse conduit 432. At that point, fluid fromthe first sub-chamber 444 is allowed to flow through the duct,transverse conduit 432, cavity 452, and another transverse conduit 432to the second sub-chamber 446, thereby equalizing the pressure in thefirst and second sub-chambers 444, 446. Similarly, as the secondactuating rod 406 is pulled in a second distal direction, the pressurein the third sub-chamber 458 may increase until the duct 466 entersfluid communication with a transverse conduit 470. At that point, fluidfrom the third sub-chamber 458 is allowed to flow to the fourthsub-chamber 460 through the duct 466, cavity 468, and another transverseconduit 470 to the fourth sub-chamber 460, thereby equalizing thepressure in the third and fourth sub-chambers 458, 460. As the spinecontinues to grow, the pressure differential between the first andsecond sub-chambers 444, 446 (and/or between the third and fourthsub-chambers 458, 460) may increase until the next transverse conduit oneither of the first or second extension members 428, 430 reaches theduct on the respective actuating rod. Advantageously, as the spine growsor lengthens, the extendable rod assembly 400 can continue to extendautomatically in this manner. Those skilled in the art may appreciatethat an equal and opposite pressure may be applied to the first andsecond actuating rods 404, 406. Accordingly, both first and secondactuating rods 404, 406 may move apart (e.g., outwards) at the samerate. Consequently, the elongate sleeve 402 may remain in the center ofthe assembly 400 (as measured, for example, along the overall length ofthe assembly). This embodiment may be particularly advantageous whentreating a curvature in the middle of a spine, e.g., in the thoracicspine. Other embodiments that include extension in only one directionmay be advantageous when treating a curvature in an upper or lowerportion of a spine, e.g., in the lumbar spine.

Turning now to FIGS. 5A-C, an alternative embodiment, extendable rodassembly 600, is illustrated. The extendable rod assembly 600 caninclude an elongate sleeve 602, an actuating rod 604, and a fixed rod606. The extendable rod assembly 600 may include a length 608 thatextends from a distal-most end 610 of the actuating rod 604 to adistal-most end 612 of the fixed rod 606. Advantageously, the length 608of the extendable rod assembly 600 may vary as the assembly 600 extendsor retracts. In some embodiments, the length 608 of the assembly 600 maybe configured to increase by about 5 to about 10 cm. In otherembodiments, the length 608 of the assembly 600 may be able to increaseby at least 7 cm. In yet other embodiments, the length 608 of theassembly 600 may be configured to increase by a factor in the range offrom about 10% to about 50%. In other embodiments, the length 608 of theassembly 600 may be configured to increase by a factor in the range offrom about 20% to about 30%. In yet other embodiments, the length 608 ofthe assembly 600 may be configured to increase by about 25%. In someembodiments, the extendable rod assembly 600 can be configured to extendlongitudinally in a straight line along its length 608. In otherembodiments, the extendable rod assembly 600 may be configured to extendalong a curved line.

As illustrated in FIGS. 5A-B, the elongate sleeve 602 may include acannula 610 extending longitudinally therethrough. The elongate sleeve602 can be cylindrical (e.g., can include a circular transverse crosssection and a constant inner and/or outer diameter). In someembodiments, the elongate sleeve 602 may have an outer diameter in therange of from about 5 mm to about 10 mm. The cannula 610 may also have acircular transverse cross section and/or a constant diameter. Asillustrated in FIGS. 5A-B, the elongate sleeve 602 may be straight(e.g., may remain longitudinally along a straight line). In otherembodiments, the elongate sleeve 602 may be curved. The elongate sleeve602 can include a first end 614 and a second end 616. In someembodiments, the first and/or second ends 614, 616 may be configured toreceive first and/or second end caps thereon. The first and/or secondends 614, 616 may be configured to engage or mate with the first andsecond end caps, and may include, for example, external threading. Insome embodiments, the second end 616 may not include external threadingand/or an end cap.

As illustrated in FIG. 5A, the first end 614 may be configured to engageor receive a seal member 618 therein. For example, the first end 614 mayinclude an internal circumferential groove, and the seal member 618 maybe disposed within the groove. The seal member may have any of theproperties as described herein with respect to seal member 22, and insome embodiments may be a wiper seal. The seal member 618 may beconfigured to prevent or reduce fluid leakage into or out of the cannula610 via the first end 614. In some embodiments, the seal member 618 mayinclude a one-way valve configured for degassing the cannula 610. Theelongate sleeve 602 may additionally include a port 620, as illustratedin FIG. 5B. The port 620 may be configured to transfer a fluid in andout of the cannula 610. The port 620 may be located at the second end616 of the elongate sleeve 602. In some embodiments, the port 620includes a conduit or hole passing through a side wall of the elongatesleeve 602. The port 620 may connect the cannula 610 with an outersurface of the elongate sleeve 602. In some embodiments, the port 620may be configured to couple directly with a fluid source.

In other embodiments, the assembly 600 may further include a fluidconnector 622. The fluid connector 622 may be configured to direct afluid into and/or out of the cannula 610 through the port 620. Asillustrated in FIG. 5B, the fluid connector 622 can include a body 624,an inflow member 626, and an outflow member 628. It is noted that theterms “inflow member” and “outflow member” are non-limiting with regardsto the direction of fluid flow within these members. As describedfurther herein, fluid may flow both into and out of the inflow memberand the outflow member, respectively. The inflow member 626 may includean inlet opening 630 and a lumen that extends from the inlet opening 630to the body 624. In some embodiments, the inflow member 626 may beconfigured to be inserted into a tube or hose of a fluid source. Forexample, the inflow member 626 may include a hollow cylinder having atapered exterior surface and at least one back-out prevention memberdisposed on the tapered exterior surface. In some embodiments, theback-out prevention member may be a slanted ring or a ridge. As anotherexample, the inflow member 626 may include a hose barb. In someembodiments, the assembly 600 may additionally include a tube or hosethat is coupled with the inflow member 626 and that is configured toreceive a fluid, e.g., via pump or injection. The inflow member 626 mayinclude a longitudinal axis that is orthogonal or perpendicular to alongitudinal axis of the outflow member 628. The outflow member 628 mayinclude an outlet opening and a lumen that extends from the outletopening to the body 624. The lumen may have a transverse cross-sectionalarea that is greater than a transverse cross-sectional area of theoutlet opening. In some embodiments, the outlet opening may include anozzle, such as a membrane nozzle. The body 624 may also include aconduit which may be in fluid communication with the lumen of the inflowmember 626 and/or the lumen of the outflow member 628. Accordingly, thefluid connector 622 may include a passageway that extends from the inletopening 630 to the outlet opening. In some embodiments, the fluidconnector 622 may include a valve configured to regulate fluid flowthrough the passageway.

As illustrated in FIG. 5B, the outflow member 628 of the fluid connector622 may be configured to engage with, e.g., be inserted into, the port620 of the elongate sleeve 602. The outflow member 628 may be reversiblyor irreversibly coupled with the port 620. For example, the outflowmember 628 may be irreversibly coupled or connected to the port 620 by amethod such as welding, soldering, or use of an adhesive. In someembodiments, the outflow member 628 may be configured engage the port620 in a friction or interference fit. In other embodiments, the outflowmember 628 may be configured to be threaded into the port 620. In theseembodiments, the port 620 may also include internal threading. In yetother embodiments, the outflow member 628 and the port 620 may beconfigured to engage one another using a cam mechanism. The extendablerod assembly 600 may additionally include a coupling member configuredto couple the outflow member 628 to the port 620 and/or to prevent orreduce leakage. Examples of suitable coupling members include, but arenot limited to, a compression fitting, a seal member, and a fastener.

At least a portion of the actuating rod 604 can be disposed within thecannula 610 at the first end 614 of the elongate sleeve 602.Additionally, a portion of the actuating rod 604 may extend distallybeyond (e.g., out of) the first end 614 of the elongate sleeve 602. Asillustrated in FIG. 5A, for example, the distal-most end 610 of theassembly 600 may also be the distal-most end of the actuating rod 604.The actuating rod 604 may extend almost all the way through the cannula610. As illustrated in FIGS. 5A-B, for example, when in the collapsedconfiguration, a proximal end 632 of the actuating rod may be near thesecond end 616. As illustrated in FIGS. 5A-C, the actuating rod 604 maybe straight (e.g., may extend longitudinally along a straight line). Inother embodiments, it may be a curved rod. As illustrated in FIGS. 5A-C,the actuating rod 604 may have a circular transverse cross-section. Inother embodiments, the actuating rod 604 may have a differentcross-sectional shape, such as triangular, square, rectangular,pentagonal, or hexagonal. In some embodiments, the actuating rod 604 canbe solid. In other embodiments, the actuating rod 604 can be hollow(e.g., can include a cannula or other passageway extending at leastpartially therethrough). In some embodiments, the actuating rod caninclude an elongate cylinder having a constant outer diameter. Thediameter of the actuating rod 604 can vary, and may be, for example, inthe range of from about 3 mm to about 10 mm. In some embodiments, thediameter of the actuating rod 604 can be in the range of from about 4 mmto about 7 mm. The outer diameter of the actuating rod 604 may be lessthan the inner diameter of the elongate sleeve 602 (e.g., less than thediameter of the cannula 610). In some embodiments, the outer diameter ofthe actuating rod 604 may be equal to or slightly less than the innerdiameter of the portion of the elongate sleeve 602 that includes theseal member 618. Accordingly, the actuating rod 604 may be engaged withthe seal member 618 in a slip fit.

As illustrated in FIG. 5B, the proximal end 632 of the actuating rod 604may be configured to engage or receive at least one seal member 634thereon. For example, the proximal end 632 may include an externalcircumferential groove, and the seal member 634 may be disposed withinthe groove. The seal member 634 may have any of the properties asdescribed herein with respect to seal member 22, and in some embodimentsmay be square ring or an o-ring. In some embodiments, the proximal end632 may be configured to receive a plurality of seal members (e.g., two,three, four, five, or more). For example, as illustrated in FIG. 5B, theproximal end 632 may be configured to receive three seal membersthereon. In these embodiments, each seal member may be staggeredlongitudinally along the actuating rod 604. The outer diameter of aportion of the actuating rod 604 having a seal member 634 disposedthereon (e.g., the combined diameter of the actuating rod 604 and theseal member 634) may be greater than a portion of the actuating rod 604that does not include a seal member, as illustrated in FIG. 5B. Thisouter diameter may also be greater than the inner diameter of theportion of the elongate sleeve 602 having seal member 618 disposedtherein. Advantageously, the seal member 618 may thereby act as astopper to prevent the proximal end 632 of the actuating rod 604 fromexiting the first end 614 of the elongate sleeve 602.

Those skilled in the art may appreciate that the actuating rod 604 maybe configured to slide and/or translate longitudinally within theelongate sleeve 602. Accordingly, the extendable rod assembly 600 can beconfigured to transition from a first configuration, wherein theassembly 600 is retracted, collapsed, shortened, un-expanded, and/orun-extended, as illustrated in FIGS. 5A-B, and a second configuration,wherein the assembly 600 is lengthened, expanded, and/or extended, asillustrated in FIG. 5C. In the first configuration, the proximal end 632of the actuating rod 604 can contact or be adjacent to the fixed rod 606and the length 608 of the assembly 600 may be minimized. In the secondconfiguration, the proximal end 632 of the actuating rod 604 may reachthe first end 614 of the elongate sleeve 602 and the length 608 of theassembly 600 may be maximized. Those skilled in the art may appreciatethat the assembly 600 may also be capable of numerous intermediateconfigurations, wherein the overall length of the assembly 600 isgreater than the fully retracted length and less than the fully extendedlength.

As illustrated in FIG. 5B, the actuating rod 604 can also include atleast one locking member 636. In some embodiments, the locking member636 may be disposed anywhere along the actuating rod 604 (e.g., aproximal, intermediate, or distal portion). As illustrated in FIG. 5B,the locking member 636 can be disposed on the proximal end 632 of theactuating rod 604. The proximal end 632 can include a tapered groove638, and the locking member 636 may be disposed within the taperedgroove 638. The tapered groove 638 may extend longitudinally along anexternal surface of the actuating rod 604. As illustrated in FIG. 5B,the tapered groove 638 may have a first depth at a proximal end 640 anda second depth at a distal end 642, wherein the first depth is greaterthan the second depth. As described further herein, the locking member636 may be configured to inhibit the actuating rod 604 from moving orsliding into the cannula 610 (e.g., may prevent or inhibit collapsing orshortening of the assembly 600). For example, the locking member 636 caninclude a spherical member 644 which may be coupled to a spring member646. In some embodiments, the locking member 636 may be a spring-loadedball. In some embodiments, the actuating rod 604 can include a pluralityof locking members 636, e.g., two, three, four, or more. In theseembodiments, the locking members 636 may be distributed around thecircumference of the proximal end 632. In other embodiments, the lockingmembers 636 may be arranged in series longitudinally on the actuatingrod 604.

As illustrated in FIG. 5A, the fixed rod 606 may include a head 648 anda body 654. At least a portion of the fixed rod 606, e.g., head 648, maybe disposed within the cannula 610 at the second end 612 of the elongatesleeve 602. As illustrated in FIG. 5B, the head 648 may include a stem650 and an intermediate portion 652. The intermediate portion 652 mayconnect the head 648 to the body 654. The stem 650 may be generallycylindrical and may have an outer diameter that is less than thediameter of the cannula 610. Advantageously, the stem 650 may be used tomaintain a gap between the actuating rod 604 and the fixed rod 606,thereby preventing the formation of a seal between these two members.The intermediate portion 652 may be configured to engage an innersurface of the elongate sleeve 602. In some embodiments, theintermediate portion 652 may also be generally cylindrical and may havean outer diameter that is slightly less than or equal to the diameter ofthe cannula 610. For example, the intermediate portion 652 may beconfigured to engage the inner surface of the elongate sleeve 602 in afriction or interference fit. In some embodiments, the intermediateportion 652 may be permanently attached or affixed within the cannula610 (e.g., via welding, soldering, or adhering). The body 654 may extendtowards the distal-most end 612, in a direction opposite of theactuating rod 604. As illustrated in FIG. SB, the body 654 may include aproximal tapered portion 656 and a distal elongate portion 658. Thetapered portion 656 may have a transverse cross-sectional area thatdecreases in the distal direction (e.g., towards the distal-most end612), and the elongate portion 658 may have a constant transversecross-sectional area. As illustrated in FIGS. 5A and C, the elongateportion 658 may be straight (e.g., may extend longitudinally along astraight line). In other embodiments, it may be curved. The elongateportion 658 may have a circular transverse cross-section. In otherembodiments, the elongate portion 658 may have a differentcross-sectional shape, such as triangular, square, rectangular,pentagonal, or hexagonal. In some embodiments, the fixed rod 606 may besolid. In other embodiments, the fixed rod 606 may be hollow (e.g., caninclude a cannula or other passageway extending at least partiallytherethrough). In some embodiments, the elongate portion 658 can includean elongate cylinder having a constant outer diameter. The diameter ofthe cylindrical portion 658 can vary, and may be, for example, in therange of from about 3 mm to about 10 mm. In some embodiments, thediameter of the cylindrical portion 658 can be in the range of fromabout 5 mm to about 7 mm. In other embodiments, the outer diameter ofthe cylindrical portion 658 of the fixed rod 606 can be the same as theouter diameter of the actuating rod 604.

Embodiments herein are also directed to methods of extending theextendable rod assembly 600. In use, the extendable rod assembly 600 maybe provided in a retracted, collapsed, shortened, and/or un-extendedconfiguration having a first length. In this configuration, the proximalend 632 of the actuating rod 604 may rest against or be adjacent to thestem 650 of the fixed rod 606. In embodiments where the extendable rodassembly 600 is being used to treat EOS, the extendable rod assembly 600may be installed along a spine in the retracted configuration asdescribed with respect to other extendable rod assemblies disclosedherein. In some embodiments, a tube or hose may be coupled with thefluid connector 622 either before or after installation of the assembly600. The tube or hose coupled with the fluid connector 622 mayadvantageously be implanted subcutaneously.

The method of extending the extendable rod assembly 600 may then includecoupling the port 620 with a fluid source. In some embodiments, the port620 may be coupled directly to a fluid source. In other embodiments, theport 620 may be coupled indirectly to a fluid source through the fluidconnector 622. For example, this step may include attaching or couplinga tube with the inflow member 626. In yet other embodiments, the port620 may be coupled indirectly to a fluid source through the fluidconnector 622 and the tube or hose coupled to the inflow member 626 ofthe fluid connector 622. For example, this step may include inserting anozzle into the tube or hose.

The method may then include the step of introducing the fluid into thecannula 610. This step can include actuating the fluid source. Variousfluids may be used to extend the extendable rod assembly 600 and may beselected on the basis of various factors, including, but not limited tocompressibility, viscosity, and thermal conductivity, as well asconsideration of the expected load or weight exerted on the assembly600. Non-limiting examples of suitable fluids include air and saline.Additionally, various sources of fluid as known to those skilled in theart may be used. For example, in some embodiments, the fluid source caninclude a pump and/or injector. In other embodiments, it can include asaline injector. The fluid source may also be actuated using anyappropriate methods, including manually and/or electronically.

In use, as the fluid enters the cannula 610, it may exert a pressure onthe actuating rod 604, causing the actuating rod 604 to translatedistally (e.g., outwards) in the direction indicated by arrow 605 and atleast partially out of the cannula 610, thereby extending the extendablerod assembly 600 to a second length that is greater than the firstlength. Those skilled in the art may appreciate that the locking member636 may not prevent motion of the actuating rod 604 in the distaldirection. As the actuating rod 604 is pushed distally, the springmember 646 may compress and the spherical member 644 may rest in thedeep proximal end 640 of the tapered groove 630.

After the assembly 600 has been extended, the fluid may optionally beremoved from the cannula 610. This step may include, for example, usinggravitational forces to allow the fluid to drain through a tube or hosethat is coupled to the port 620, either directly or indirectly via thefluid connector 622. In other embodiments, this step may includeapplying a vacuum or other source of negative pressure to actively pumpthe fluid out. As the fluid is removed or drained, the locking member636 may advantageously prevent the actuating rod 604 from retractingback into the cannula 610. For example, as the actuating rod 604 ispulled proximally, the spherical member 644 may roll towards the shallowdistal end 642 of the tapered groove 638. While in the shallow part ofthe groove 638, the spherical member 644 may engage or contact the innersurface of the elongate sleeve 602 in an interference or friction fit,thereby inhibiting further movement of the actuating rod 604 in theproximal direction. As described herein, in embodiments that include atube or hose coupled with the fluid connector 622, the tube or hose maybe implanted subcutaneously. Thus, subsequent lengthening procedures(e.g., every three to six months) may be advantageously performed in asubcutaneous and/or minimally-invasive procedure. Such a procedure mayrequire less time for surgery and recovery as compared to a moreinvasive extension procedure, and may also reduce risks to a patient.

Turning now to FIGS. 6A-F, an alternative embodiment, extendable rodassembly 800, is illustrated. As illustrated in FIG. 6A, the extendablerod assembly 800 can include an elongate sleeve 802, an actuating rod804, and a fixed rod 806. The elongate sleeve 802 can include a conduit808 extending therethrough from a first end 810 to a second end 812. Theelongate sleeve 802 can also include a housing member 814. Asillustrated in FIG. 6B, the housing member 814 may be disposed on theelongate sleeve 802. In other embodiments, the housing member 814 may beintegral with the elongate sleeve 802. In yet other embodiments, thehousing member 814 may be reversibly coupled with the elongate sleeve802. The housing member 814 may include a cavity 840 in fluidcommunication with the conduit 808. As illustrated in FIGS. 6A-B, forexample, the elongate sleeve 802 may be generally cylindrical (e.g., mayhave a circular transverse cross-section, and may include a constantinner and/or outer diameter). In some embodiments, the elongate sleeve802 may have an outer diameter in the range of from about 5 mm to about10 mm. The elongate sleeve 802 may extend longitudinally along astraight or curved line (e.g., can accommodate a straight or curvedrod).

As described further with respect to an alternative embodiment, elongatesleeve 803, the elongate sleeve 802 may include at least one guidemember disposed within the conduit 808, e.g., at the first end 810. Theguide member may include a channel configured to receive the actuatingrod 804 therethrough. Advantageously, the guide member may be configuredto stabilize the actuating rod 804 as it translates through the elongatesleeve 802, as described further herein. The elongate sleeve 802 mayalso include a retaining member disposed within the conduit 808, e.g.,at the second end 812, and that may be configured to secure the fixedrod 806 within the elongate sleeve 802. The elongate sleeve 802 may alsobe configured to couple with one or more seal members. For example, insome embodiments, the first end 810 and/or the second end 812 of theelongate sleeve 802 may include an internal circumferential grooveconfigured to receive a seal member therein. In some embodiments, theinternal circumferential groove may be disposed on the guide member. Theseal member may be, for example, an o-ring, a square ring, or any otherseal members as described herein.

In some embodiments, the elongate sleeve 802 may include a cover. Asillustrated in FIG. 6C, the housing member 814 may include a cover 816.An alternative embodiment, elongate sleeve 803 including cover 817, isillustrated in FIGS. 6E-F. The cover 816 may be configured to shield,protect, or enclose the housing member 814. The cover 816 may beconfigured to permanently or irreversibly mate with or engage thehousing member 814, e.g., by welding, soldering, or adhering. In otherembodiments, the cover 816 may be configured to temporarily orreversibly mate with or engage the housing member 814, e.g., by the useof fasteners or a snap fit between the two components. In someembodiments, the assembly 800 may include a seal member between thehousing member 814 and the cover 816. The cover 816 may include anaperture 818. The aperture 818 may be configured to receive a drivemember 820 therein. The drive member 820 may be rotatably disposedwithin the aperture 818. The drive member 820 may be configured toengage a gear assembly, described further herein, and/or a driver. Insome embodiments, the drive member 820 may include a driver interfacesection 822 and a gear interface section. As illustrated in FIG. 6C, thedriver interface section 822 may be configured to extend out of thehousing member 814. The driver interface section 822 may include aprotrusion, as illustrated in FIG. 6C, or a socket, as illustrated inFIG. 6F. The driver interface section 822 may include a transversecross-sectional shape selected from the group consisting of circular,triangular, square, rectangular, pentagonal, and hexagonal. In someembodiments, the driver interface section 822 may include a hexagonalprotrusion, as illustrated in FIG. 6C, or a hexagonal socket, asillustrated in FIG. 6F with regards to driver member 821. The aperture818 may also be configured to receive a seal member. The seal member mayadvantageously prevent, reduce, or inhibit leakage into or out of thehousing member 814 via the aperture 818.

An alternative embodiment of an elongate sleeve 803 is illustrated inFIGS. 6E-F. In this embodiment, the elongate sleeve 803 may include ahousing member 815 that is integral with the elongate sleeve 803.Additionally, in these embodiments, the elongate sleeve 803 may notinclude an enclosed tube. Accordingly, the elongate sleeve 803 may alsoinclude a cover 817 that is configured to shield, protect, or encloseboth the conduit 809 of the elongate sleeve 803 and the cavity 841 ofthe housing member 815. Except as otherwise described, the elongatesleeve 803 and its associated components (including, but not limited to,housing member 815, cover 817, and drive member 821) may include one ormore of the same features as the elongate sleeve 802 and its associatedcomponents (including, but not limited to, housing member 814, cover816, and drive member 820). For example, the elongate sleeve 803 mayinclude one or more guide members 819. Each guide member 819 may includea channel 823 configured to receive the actuating rod 804 therethrough.

As illustrated in FIGS. 6B and 6E, the extendable rod assembly 800 mayfurther include a gear assembly 824. The gear assembly 824 may bedisposed or mounted in the housing member 814 or 815. The gear assembly824 may be configured to actuate or translate the actuating rod 604, forexample, using a rack and pinion mechanism. In some embodiments, thegear assembly 824 can include one gear. In other embodiments, the gearassembly 824 can include a series of gears, e.g., a gear train that caninclude two, three, four, or more gears. As illustrated in FIG. 6B, thegear train can include an input gear 826 and an output gear 828. Theinput gear 826 can be configured to engage the drive member 820 or 821.For example, the input gear 826 can include a socket 830 that isconfigured to receive the drive member 820 or 821. The output gear 828may be configured to engage the actuating rod 804. For example, theoutput gear 828 may have teeth that are configured to mesh with teeth onthe actuating rod 804. The output gear 828 may be referred to as apinion.

In some embodiments, the gear assembly 824 can include four gears. Inthese embodiments, two of the four gears may be joined or affixedtogether as a compound gear 832. The compound gear 832 may include afirst, larger gear 834 sharing an axle with and/or mounted on a second,smaller gear, wherein the larger gear 834 is configured to mesh with theinput gear 826 and the smaller gear is configured to mesh with theoutput gear 828. The input gear 826 and the second, smaller gear mayeach have a number of teeth that is half of that of the larger gear 834and the output gear 828. For example, the input gear 826 and the smallergear may each include sixteen teeth, and the output gear 828 and thelarger gear 834 may each include thirty-two teeth. In these embodiments,the gear train may have a gear ratio of 4:1.

In other embodiments, the gear assembly 824 can include three gears. Inthese embodiments, the gear train may include input gear 826, outputgear 828, and an idler gear (not shown). The idler gear may beconfigured to mesh with both the input gear 826 and the output gear 828.The input gear 826 and the idler gear may each have a number of teeththat is half of that of the output gear 828. For example, the input gear826 and the idler gear may each have sixteen teeth and the output gear828 may include thirty-two teeth. In these embodiments, the gear trainmay have a gear ratio of 2:1.

When turned in a clockwise motion, the input gear 826 may cause theactuating rod 804 to translate distally out of the elongate sleeve 802.The gear assembly 824 may be configured such that one revolution of thedrive member 820 or 821 can cause the actuating rod 804 to translate bya distance in the range of from about 4 mm to about 12 mm. In otherembodiments, one revolution of the drive member 820 or 821 may cause theactuating rod 804 to translate by a distance in the range of from about4 mm to about 6 mm. In yet other embodiments, one revolution of thedrive member 820 or 821 may cause the actuating rod 804 to translate bya distance in the range of from about 9 mm to about 12 mm. In someembodiments, one revolution of the driver member 820 or 821 maygenerally approximate the estimated growth of a spine over a particularperiod, such as three months or six months. Overall, the length of theassembly 800, as measured from a distal-most end 805 of the actuatingrod 804 to a distal-most end 807 of the fixed rod 806, may be configuredto vary by an amount in the range of from about 5 cm to about 10 cm. Forexample, the assembly 800 may be configured to lengthen or extend by atleast 7 cm. In yet other embodiments, the length of the assembly 800 maybe configured to increase by a factor in the range of from about 10% toabout 50%. In other embodiments, the length of the assembly 800 may beconfigured to increase by a factor in the range of from about 20% toabout 30%. In yet other embodiments, the length of the assembly 800 maybe configured to increase by about 25%.

Any drivers known in the art may be used to drive or rotate the drivemember 820 or 821. In some embodiments, the driver may be actuated by amotor that may be coupled to a computer system or other electronics. Inthese embodiments, the driver may be incorporated into the assembly 800(e.g., mounted in or on the elongate sleeve 802) or may be reversiblycoupled with the assembly 800. In other embodiments, the driver, andconsequently, the gear assembly 824, may be configured to be actuatedmanually, e.g., by hand. In these embodiments, the gear assembly 824 maybe configured such that the amount of torque that is required to rotatethe drive member and extend the actuating rod 804, while alsocounteracting any compressive or distractive forces within a spinalcolumn, is within the range of a reasonable manual output, e.g., fromabout 1 N·m to about 10 N·m. For example, the gear assembly describedherein having a gear ratio of 4:1 may be configured to be actuated uponreceiving an input of about 2.5 N·m of torque. The gear assemblydescribed herein having a gear ratio of 2:1 may be configured to beactuated upon receiving an input of about 5 N·m of torque. Those skilledin the art may appreciate that other gear sizes, combinations, and/orratios may be utilized to vary the rate at which the assembly 800lengthens (e.g., the rate at which the actuating rod 804 translates)and/or the input force required per revolution.

In some embodiments, the gear assembly 824 may further include a lockingmember, which may be configured to prevent translation of the actuatingrod in a proximal (e.g., inward) direction. The locking member may be aspring-loaded pawl. The locking member may be coupled to the input gear826 or its axle, and may be configured to directly engage the smallermember of the compound gear 832 or the idler gear. The locking membermay be coupled to a lever, wherein the lever may be configured todisengage the locking member. The lever may be configured to be actuatedby a driver, and in some embodiments, can be accessed through the socket830. In use, if the assembly 800 needs to be shortened or retracted, adriver can be inserted into the socket 830 to activate (e.g., depress)the lever, thereby releasing the locking member and allowing gear trainto rotate in reverse such that the actuating rod translates into theelongate sleeve 802.

As illustrated in FIG. 6B, the actuating rod 804 may include a pluralityof gear teeth 836 thereon. In some embodiments, the actuating rod 804may include a toothed section and one or more smooth or non-toothedsections 838, as illustrated in FIG. 6D. The actuating rod 804 may be atleast partially disposed within a portion of the conduit 808 of theelongate sleeve 802, e.g., the first end 810, and may extend in a firstdirection. Additionally, a portion of the actuating rod 804 may extenddistally beyond the first end 810 of the conduit 808. The distal-mostend of the assembly 800 may also be the distal-most end of the actuatingrod 804. As illustrated in FIGS. 6A-D, the actuating rod 804 may bestraight (e.g., may extend longitudinally along a straight line). Inother embodiments, it may be a curved rod. The smooth or non-toothedsection 838 may have a circular transverse cross-section and/or caninclude an elongate cylinder having a constant outer diameter. In otherembodiments, it may have a different cross-sectional shape, such astriangular, square, rectangular, pentagonal, or hexagonal. In someembodiments, the actuating rod 804 can be solid. In other embodiments,the actuating rod 804 can be hollow (e.g., can include a cannula orother passageway extending at least partially therethrough). Thediameter of the actuating rod 804 can vary, and may be, for example, inthe range of from about 3 mm to about 10 mm. In some embodiments, thediameter of the actuating rod 804 can be in the range of from about 4 mmto about 7 mm. As described herein, the gear assembly 824 may beconfigured to engage the actuating rod 804. In some embodiments, thegear assembly 824 and the actuating rod 804 may be configured for directengagement, e.g., meshing the teeth on the output gear 828 and the teeth836 on the actuating rod 804. As described herein, the actuating rod 804may be held within the conduit 808 by one or more guide members (e.g.,guide member 819).

Those skilled in the art may appreciate that the actuating rod 804 maybe configured to slide and/or translate longitudinally within theelongate sleeve 802. Accordingly, the extendable rod assembly 800 can beconfigured to transition from a first configuration, wherein theassembly 800 is retracted, collapsed, shortened, un-expanded, and/orun-extended, as illustrated in FIGS. 6A-C, and a second configuration,wherein the assembly 800 is lengthened, expanded, and/or extended, asillustrated in FIG. 5D. In the first configuration, a proximal end ofthe actuating rod 804 can contact or be adjacent to a proximal end ofthe fixed rod 806 and an overall length of the assembly 800 may beminimized. In the second configuration, the proximal end of theactuating rod 804 may reach the first end 810 of the elongate sleeve 802and the overall length of the assembly 800 may be maximized. In someembodiments, the assembly 800 may have a length in the range of fromabout 20 cm to about 25 cm when in the first configuration and a lengthin the range of from about 27 cm to about 32 cm when in the secondconfiguration. Those skilled in the art may appreciate that the assembly800 may also be capable of numerous intermediate configurations, whereinthe overall length of the assembly 800 is greater than the fullyretracted length and less than the fully extended length.

As illustrated in FIGS. 6A and 6D, the fixed rod 806 may include acylinder having a circular transverse cross-section and/or a constantouter diameter. The fixed rod 806 may be at least partially disposedwithin the second end 812 of the conduit 808 and may extend in a seconddirection, e.g., opposite to that of the actuating rod 804.Additionally, a portion of the fixed rod 806 may extend distally beyondthe second end 812 of the conduit 808. The fixed rod 806 may be held orsecured within the conduit 808 by one or more guide members (e.g., guidemember 819). The fixed rod 806 may be straight (e.g., may extendlongitudinally along a straight line). In other embodiments, it may becurved. The fixed rod 806 may have a circular transverse cross-section.In other embodiments, the fixed rod 806 may have a differentcross-sectional shape, such as triangular, square, rectangular,pentagonal, or hexagonal. In some embodiments, the fixed rod 806 may besolid. In other embodiments, the fixed rod 806 may be hollow (e.g., caninclude a cannula or other passageway extending at least partiallytherethrough). In some embodiments, the fixed rod 806 can include anelongate cylinder having a constant outer diameter. The diameter of thefixed rod 806 can vary, and may be, for example, in the range of fromabout 3 mm to about 10 mm. In some embodiments, the diameter of thefixed rod 806 can be in the range of from about 5 mm to about 7 mm. Inother embodiments, the outer diameter of the fixed rod 806 can be thesame as the outer diameter of the actuating rod 804. Those skilled inthe art may appreciate that in other embodiments, the fixed rod 806 maybe configured to translate, e.g., by adding gear teeth thereon that areaccessible by a gear assembly, such that the assembly 800 can extend orelongate from both ends.

Embodiments herein are also directed to methods of extending theextendable rod assembly 800. In use, the extendable rod assembly 800 maybe provided in a retracted, collapsed, shortened, and/or un-extendedconfiguration having a first length, as illustrated, for example, inFIG. 6A. In embodiments where the extendable rod assembly 800 is beingused to treat EOS, the extendable rod assembly 800 may be installedalong a spine in the retracted configuration as described with respectto other extendable rod assemblies disclosed herein.

The method of extending the extendable rod assembly 800 may then includecoupling a driver with the drive member 820 or 821. As described herein,any driver known in the art and configured to engage and apply torque tothe drive member may be used. For example, in some embodiments thedriver can include a wrench member, such as an Allen wrench or hex key,or a socket wrench member, such as a hex socket wrench. The method maythen include applying torque to the drive member 820 or 821 in a firstdirection (e.g., clockwise). As illustrated in FIG. 6B, as the drivemember turns clockwise, it can engage the input gear 826, which can alsoturn clockwise. This may cause the compound gear 832 (or idler gear) toturn counterclockwise and engage the output gear 828. This may cause theoutput gear 828 to turn clockwise, thereby engaging the teeth 836 on theactuating rod 804 and pushing the actuating rod 804 distally (e.g., outof the elongate sleeve 802). As described herein, the gear assembly 824may advantageously be configured so that one revolution of the drivemember 820 or 821 results in a lengthening of the extendable rodassembly 800 by an amount in the range of 5 mm to 10 mm. The lockingmember may prevent the actuating rod 804 from retracting back into theconduit 808 or 809. However, if the assembly 800 needs to be shortened,it may be reduced by disengaging the locking member and applying torqueto the drive member in a second, opposite direction (e.g.,counterclockwise). In use, a driver, which may be the same or differentdriver used to extend the assembly 800, may push the drive member 820 or821 into the socket 830 of the input gear 826 until it engages thelatch, thereby disengaging the locking member from the compound gear 832(or idler gear). Once the locking member is disengaged, the driver mayrotate the drive member 820 or 821 in a counterclockwise direction,which can thereby cause the actuating rod 804 to retract proximally intothe conduit 808 or 809.

In some embodiments, the extendable or growing rods described above canbe used with various other spinal implants, including but not limited tofusion devices and prosthetic devices. Fusion devices include cages,spacers (expandable and non-expandable), biological material (e.g.,graft material inserted into the cages and spacers), corpectomy devices,plates, rod members and various fixation devices, including pediclescrews and hooks. Prosthetic devices include artificial discs, facetjoint replacements, and any other implant that mimics anatomical motion.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims. Althoughindividual embodiments are discussed herein, the invention covers allcombinations of all those embodiments.

1. An extendable rod assembly, comprising: an elongate sleeve having alongitudinal axis comprising a conduit extending therethrough, andfurther comprising a housing member in fluid communication with theconduit, the housing member being offset from the longitudinal axis; agear assembly disposed within the housing member; an actuating rod atleast partially disposed within the conduit and extending in a firstdirection, the actuating rod comprising a plurality of teeth configuredto mesh with a member of the gear assembly; and a fixed rod at leastpartially disposed within the conduit and extending in a seconddirection.
 2. The extendable rod assembly of claim 1, wherein the gearassembly comprises a gear train, the gear train comprising an input gearand an output gear.
 3. The extendable rod assembly of claim 2, whereinthe input gear comprises a socket configured to receive a drive member.4. The extendable rod assembly of claim 2, wherein one revolution of theinput gear is configured to translate the actuating rod by a distance inthe range of from 4 mm to 12 mm.
 5. The extendable rod assembly of claim2, wherein one revolution of the input gear is configured to translatethe actuating rod by a distance in the range of from 9 mm to 12 mm. 6.The extendable rod assembly of claim 2, wherein the output gear isconfigured to engage the actuating rod.
 7. The extendable rod assemblyof claim 2, wherein the gear train further comprises a compound gearconfigured to couple with the input gear and the output gear.
 8. Theextendable rod assembly of claim 7, wherein the gear assembly furthercomprises a locking member configured to prevent translation of theactuating rod in a proximal direction.
 9. The extendable rod assembly ofclaim 8, wherein the locking member comprises a spring-loaded pawl. 10.The extendable rod assembly of claim 9, wherein the locking member isconfigured to directly engage the compound gear.
 11. The extendable rodassembly of claim 8, further comprising a lever configured to disengagethe locking member.
 12. An extendable rod assembly, comprising: anelongate sleeve having a longitudinal axis comprising a conduitextending therethrough and a housing member disposed thereon, whereinthe housing member is in fluid communication with the conduit; a gearassembly mounted in the housing member, the housing member being offsetfrom the longitudinal axis; an actuating rod at least partially disposedwithin the conduit and extending in a first direction; and a fixed rodat least partially disposed within the conduit and extending in a seconddirection; wherein a member of the gear assembly is configured todirectly engage the actuating rod.
 13. The extendable rod assembly ofclaim 12, wherein at least one of the elongate sleeve and the housingmember comprises a cover.
 14. The extendable rod assembly of claim 13,further comprising a drive member coupled with the housing member andconfigured to engage the gear assembly.
 15. The extendable rod assemblyof claim 14, wherein the cover comprises an aperture, and the drivemember is rotatably disposed within the aperture.
 16. The extendable rodassembly of claim 15, wherein the drive member comprises a driverinterface section and a gear interface section, and wherein the driverinterface section is configured to extend out of the housing member. 17.An extendable rod assembly, comprising: an elongate sleeve having alongitudinal axis comprising a conduit extending therethrough from afirst end to a second end; an actuating rod comprising a plurality ofgear teeth and at least partially disposed within the first end of theconduit; a fixed rod at least partially disposed within the second endof the conduit; and a gear assembly offset from the longitudinal axisconfigured to actuate the actuating rod.
 18. The extendable rod assemblyof claim 17, wherein the assembly is non-ferromagnetic.
 19. Theextendable rod assembly of claim 18, wherein the elongate sleevecomprises at least one guide member disposed within the conduit.
 20. Theextendable rod assembly of claim 19, wherein the guide member comprisesa channel configured to receive the actuating rod therethrough.